• Communications for Statistical Applications and Methods
• /
• 제20권6호
• /
• pp.455-466
• /
• 2013

In nested case-control studies, the most common way to make inference under a proportional hazards model is the conditional logistic approach of Thomas (1977). Inclusion probability methods are more efficient than the conditional logistic approach of Thomas; however, the epidemiology research community has not accepted the methods as a replacement of the Thomas' method. This paper promotes the inverse probability weighting method originally proposed by Samuelsen (1997) in combination with an approximate jackknife standard error that can be easily computed using existing software. Simulation studies demonstrate that this approach yields valid type 1 errors and greater powers than the conditional logistic approach in nested case-control designs across various sample sizes and magnitudes of the hazard ratios. A generalization of the method is also made to incorporate additional matching and the stratified Cox model. The proposed method is illustrated with data from a cohort of children with Wilm's tumor to study the association between histological signatures and relapses.

• 한국융합학회논문지
• /
• 제10권11호
• /
• pp.501-510
• /
• 2019

본 논문은 당뇨병의 관리전략 수립을 위해 일상생활에서 조절가능한 혈당조절 요인을 파악하고자 하였다. 개인이 조절하기 어려운 성별, 당뇨병 유병기간, 당뇨병 치료방법, 교육수준, 가구소득 등을 매칭한 코호트내 환자-대조군 디자인으로 분석을 하였다. 7기 국민건강영양조사(2016-2017) 원시자료를 이용하여, 983명의 당뇨병 환자를 분석한 결과, 289명(30%)만이 당화혈색소가 6.5% 미만으로 혈당이 조절되었다. 일상생활에서 조절이 가능한 당화혈색소 조절 요인 파악하기 위해 조건부 다변량 로짓스틱 회귀분석 시행한 결과, 매칭전 코호트에서는 당뇨병 유병기간, 당뇨병 치료 여부, 매칭 코호트에서는 체질량지수, 흡연, 안저검사가 당화혈색소 달성에 유의한 영향을 미치는 것으로 파악되었다. 본 결과는 집중 관리가 필요한 대상선정(장기 유병기간, 약물치료 대상자) 및 생활습관(체질량지수, 흡연, 안저검사 등) 관리전략을 마련하는데 근거자료로 활용되고, 지역사회내 국민건강 증진에 기여할 것으로 사료된다.

• Asian Pacific Journal of Cancer Prevention
• /
• 제15권3호
• /
• pp.1497-1500
• /
• 2014

Cervical cancer continues to be an important public health problem in Thailand. While the high risk human papillomavirus (HPV) types have been established as the principle causative agent of both malignancies and the precursor lesions, cervical intraepithelial neoplasia (CIN), other factors may also be involved like other sexually transmitted diseases, as well as smoking. Chlamydia trachomatis is an obligate intracellular Gramnegative bacterium which has a tendency to cause chronic infection featuring inflammation and therefore might be expected to increase the risk of cervical cancer. In the present nested case-control study, 61 cases of cervical cancer and 288 matched controls with original serum samples were identified from the Khon Kaen Cohort, established in the North-East of Thailand, by linkage to the Khon Kaen population based cancer registry. C. trachomatis specific IgG antibodies at recruitment were measured by microimmunofluorescence and assessed for association with cervical cancer using STATA release10. No significant link was noted either with all cancers or after removal of adenocarcinomas. The results suggest no association between Chlamydia infection and cervical cancer development in North-East Thailand, but possible influencing factors must be considered in any future research on this topic.

• 컴퓨터교육학회논문지
• /
• 제19권1호
• /
• pp.101-109
• /
• 2016

컴퓨팅 사고 교육에서 알고리즘의 설계는 학습자의 논리적 사고력과 절차적 사고력이 요구되는 중요한 학습 과정이다. 하지만 알고리즘 학습에 관한 연구와 학습자가 실제 학습에서 겪는 오류에 관한 연구가 부족한 실정이다. 이에 본 연구는 알고리즘 설계 학습에서 순서도를 활용한 프로그래밍 제어 구조 설계에서 발견된 학습자의 오류를 분석하여, 오류 유형을 제시하였다. 대학생을 대상으로 한 강의에서 세 가지 제어 구조에 관한 평가 문항을 제시한 결과, 순차 구조에서는 오류 유형이 발견되지 않았다. 하지만 조건 구조에서는 2개의 조건문이 중첩된 경우 조건 설정에서 오류가 발생하였다. 반복 구조에서는 반복의 횟수를 조절하는 조건, 반복되는 명령문의 위치, 중첩된 반복문에서 조건과 명령문의 위치 오류가 발견되었다. 본 연구에서 나타난 오류 유형은 초 중등학교와 대학에서 실시하고 있는 컴퓨팅 사고 교육의 알고리즘 설계 학습에 참고할 수 있는 사례가 될 것이다.

• Asian Pacific Journal of Cancer Prevention
• /
• 제16권11호
• /
• pp.4699-4704
• /
• 2015

Medical diagnostic X-ray workers are one occupational group that expose to the long-term low-dose external radiation over their working lifetime, and they may under risk of different cancers. This study aims to determine the relationship between the occupational X-ray radiation exposure and cancer risk among these workers in Jiangsu, China. We conducted Nested case-control study to investigate the occupational X-ray radiation exposure and cancer risk. Data were collected through self-administered questionnaire, which includes but not limits to demographic data, personal behaviors and family history of cancer. Retrospective dose reconstruction was conducted to estimate the cumulative doses of the x-ray workers. Inferential statistics, t-test and 2 tests were used to compare the differences between each group. We used the logistic regression model to calculate the odds ratio (OR) and 95% confidence interval (CI) of cancer by adjusting the age, gender. All 34 breast cancer cases and 45 esophageal cancer cases that detected in a cohort conducted among health workers between 1950~2011 were included in this presented study, and 158 cancer-free controls were selected by frequency-matched (1:2). Our study found that the occupational radiation exposure was associated with a significantly increased cancer risk compared with the control, especially in breast cancer and esophageal cancer (adjusted OR=2.90, 95% CI: 1.19-7.04 for breast cancer; OR=4.19, 95% CI: 1.87-9.38 for esophageal cancer, and OR=3.43, 95% CI: 1.92-6.12 for total cancer, respectively). The occupational X-ray radiation exposure was associated with increasing cancer risk, which indicates that proper intervention and prevention strategies may be needed in order to bring down the occupational cancer risk.

• Journal of Preventive Medicine and Public Health
• /
• 제34권2호
• /
• pp.149-156
• /
• 2001

Objective : To elucidate risk factors for coronary heart diseases among Korean males. Methods : A nested case control study was conducted among a Korea Medical Insurance Cooperation(KMIC) cohort composed of 108,802 males. The eases included 246 male patients who were admitted to hospital due to coronary heart diseases from 1993 to 1997 (120-25 by ICD) and whose diagnosis was confirmed by the protocol by WHO MONICA Project(1994). The control group was composed of 483 patients selected by frequency matching considering age and resident area from an inpatient care group without coronary heart disease during the same period. For study cases and the controls, the results of a health check-up in 1990 and a questionnaire on life style in 1992 were received through the KMIC. Some additional information was collected by telephone interviews during October 1999. Results : Multiple logistic regression analysis showed that the odds ratio(OR) of coronary heart diseases among past smokers and current smokers as compared to non-smokers were 1.94(95% CI : 1.14-3.31) and 2.20(55% CI : 1.35-3.59), respectively. The OR among persons who drank 4 cups or more of caffeinated beverages such as coffee or tea daily as compared to persons who drank one cup for 2-3 days was 2.50(95% CI : 1.07-6.12). The OR among persons with high normal BP and stage 3 hypertension against normotension were 2.51 (95% CI : 1.44-4.37) and 5.08(95% CI : 2.38-10.84). The OR among persons whose blood cholesterol were 240 mg/dL or mere against lower than 200mg/dL was 2.24(95% CI : 1.43-3.49). Conclusion : Smoking, drinking of excessive caffeinated beverages, hypertension and high blood cholesterol were proven to be significant risk factors for coronary heart diseases among Korean males.

• Journal of Preventive Medicine and Public Health
• /
• 제49권2호
• /
• pp.134-138
• /
• 2016

Objectives: Season of birth, an exogenous indicator of early life environment, has been related to higher risk of adverse psychiatric outcomes but the findings for Alzheimer's disease (AD) have been inconsistent. We investigated whether the month or season of birth are associated with AD. Methods: A nationwide nested case-control study including all community-dwellers with clinically verified AD diagnosed in 2005 to 2012 (n=70 719) and up to four age- sex- and region of residence-matched controls (n=282 862) residing in Finland. Associations between month and season of birth and AD were studied with conditional logistic regression. Results: Month of birth was not associated with AD (p=0.09). No strong associations were observed with season (p=0.13), although in comparison to winter births (December-February) summer births (June-August) were associated with higher odds of AD (odds ratio, 1.03; 95% confidence interval, 1.00 to 1.05). However, the absolute difference in prevalence in winter births was only 0.5% (prevalence of those born in winter were 31.7% and 32.2% for cases and controls, respectively). Conclusions: Although our findings do not support the hypothesis that season of birth is related to AD/dementia risk, they do not invalidate the developmental origins of health and disease hypothesis in late-life cognition. It is possible that season does not adequately capture the early life circumstances, or that other (postnatal) risk factors such as lifestyle or socioeconomic factors overrule the impact of prenatal and perinatal factors.

• Journal of Preventive Medicine and Public Health
• /
• 제32권4호
• /
• pp.513-525
• /
• 1999

Objectives : High-normal blood pressure' is a factor influencing decision to initiate targeted intensive intervention strategy in westernized populations. JNC-VI offered the vigorous lifestyle modification for persons with 'high-normal blood pressure', who could be early detected. As a hypertension seems to be the result of multiple genetic factors operating in concert with associated environmental factors, it will be necessary to identify the high-normal blood pressure as a risk factor of hypertension for applying primary prevention strategy in Korean people. Methods : Although cohort study design might be adequate to recruit incidence cases, to keep time sequence of events, and to prevent information bias, nested case-control study was chosen for avoiding measurement errors because hypertension is a benign disease. Source population was the 'Seoul Cohort' participants and follow-up was done by using Korea Medical Insurance Corporation's database on the utilization of health services from 1 Jan93 to 30Jun97. Incidence cases were ascertained through the chart review, telephone contacts, and direct blood pressure measurements. Controls included the pairing of 4 individuals to each case on the basis of age. Results : As 75% of 247 incident cases had high-normal blood pressure, the crude odds ratio for hypertension was 2.04 (95% CI 1.47-2.83). Another statistically significant risk factors of hypertension were body mass index, dietary fiber, alcohol consumption, weekly activity and history of quitting smoking. The multivariate odds ratio of high-normal blood pressure adjusted for all risk factors was 1.84 (95% CI 1.31-2.56). Among high-normal blood pressure group, body mass index, weekly ethanol amounts, weekly physical activity, and dietary fiber except history of quitting smoking were still risk factors of hypertension. Conclusion : 'High-normal blood pressure' is a risk factor for hypertension in Korean middle-aged men, which represents that the vigorous lifestyle modification for persons with 'high-normal blood pressure' is need.

• 산업경영시스템학회지
• /
• 제37권4호
• /
• pp.35-41
• /
• 2014

Real-life time series characteristic data has significant amount of non-stationary components, especially periodic components in nature. Extracting such components has required many ad-hoc techniques with external parameters set by users in a case-by-case manner. In this study, we used Empirical Mode Decomposition Method from Hilbert-Huang Transform to extract them in a systematic manner with least number of ad-hoc parameters set by users. After the periodic components are removed, the remaining time-series data can be analyzed with traditional methods such as ARIMA model. Then we suggest a different way of setting control chart limits for characteristic data with periodic components in addition to ARIMA components.

• Asian Pacific Journal of Cancer Prevention
• /
• 제16권18호
• /
• pp.8253-8258
• /
• 2016

Elevated levels of soluble CD30 (sCD30) are linked with various T-cell neoplasms. However, the relationship between sCD30 levels and the development of adult T-cell leukemia (ATL) in human T-cell leukemia virus type 1 (HTLV-1) carriers remains to be clarified. We here investigated whether plasma sCD30 is associated with risk of ATL in a nested case-control study within a cohort of HTLV-1 carriers. We compared sCD30 levels between 11 cases (i.e., HTLV-1 carriers who later progressed to ATL) and 22 age-, sex- and institution-matched control HTLV-1 carriers (i.e., those with no progression). The sCD30 concentration at baseline was significantly higher in cases than in controls (median 65.8, range 27.2-134.5 U/mL vs. median 22.2, range 8.4-63.1 U/mL, P=0.001). In the univariate logistic regression analysis, a higher sCD30 (${\geq}30.2U/mL$) was significantly associated with ATL development (odds ratio 7.88 and the 95% confidence intervals 1.35-45.8, P = 0.02). Among cases, sCD30 concentration tended to increase at the time of diagnosis of aggressive-type ATL, but the concentration was stable in those developing the smoldering-type. This suggests that sCD30 may serve as a predictive marker for the onset of aggressive-type ATL in HTLV-1 carriers.